Short answers, pulled from the story.
Operation Sledgehammer was a planned World War II military operation intended to invade mainland Europe through the English Channel in 1942. The plan aimed to capture French cities such as Brest or Cherbourg to serve as staging grounds for more extensive operations.
President Franklin Roosevelt wrote a letter to British Prime Minister Winston Churchill urging immediate movement by March 1942. This correspondence occurred after the United States entered World War II in December 1941 and pushed for an invasion of mainland Europe.
General George C. Marshall and Harry Hopkins presented both plans including Operation Roundup and Operation Sledgehammer on April 8 when they arrived in Britain. Soviet Foreign Minister Vyacheslav Molotov also tried to convince both British and American officials to act during this period.
British officials concluded that landing in France at that time was premature due to overwhelming German resistance and dangerous risks. They viewed the potential failure as too high given the lack of sufficient resources available in 1942.
The British proposal for an invasion of French North Africa replaced the cancelled European landing entirely under the code name Operation Torch. Eisenhower told Churchill in November 1942 that no major operation on the Continent could be carried out before 1944.